Satellite detection of soil moisture related water stress impacts on ecosystem productivity using the MODIS-based photochemical reflectance index

Abstract

Satellite remote sensing provides continuous observations of vegetation properties that can be used to estimate global terrestrial ecosystem gross primary production (GPP). The Photochemical Reflectance Index (PRI) has been shown to be sensitive to vegetation photosynthetic light use efficiency (LUE), GPP and canopy water-stress. Here, we use the NASA EOS MODIS (Moderate Resolution Imaging Spectroradiometer) based PRI with eddy covariance CO 2 flux measurements and meteorological observations from 20 tower sites representing major plant functional type (PFT) classes within the continental USA (CONUS) to assess GPP sensitivity to soil moisture related water stress. The sPRI (scaled PRI) metric derived using MODIS band 13 as a reference channel (sPRI 13) shows generally higher correspondence with tower GPP observations than other potential MODIS reference bands. The sPRI 13 observations were used as a proxy for soil moisture related water supply constraints to LUE within a satellite data driven terrestrial carbon flux model to estimate GPP (GPP PRI). The GPP PRI calculations show generally favorable correspondence with tower GPP observations (0.457 ≤ R 2 ≤ 0.818), except for lower GPP PRI performance over evergreen needleleaf forest (ENF) sites. A regional model sensitivity analysis using the sPRI 13 as a water supply proxy indicated that water restrictions limit GPP over more than 21% of the CONUS domain, particularly in drier climate areas where atmospheric moisture (VPD) deficits alone are insufficient to represent both atmosphere demand and water supply controls affecting productivity. Our results indicate strong potential of the MODIS sPRI 13 to represent soil moisture related water supply controls influencing photosynthesis, with enhanced (1-km resolution) delineation of these processes closer to the scale of in situ tower observations. These observations may provide an effective tool for characterizing sub-grid spatial heterogeneity in soil moisture related controls that inform coarser scale observations and estimates determined from other satellite observations and global carbon, and climate models.

Photochemical Reflectance Index (PRI) for Detecting Responses of Diurnal and Seasonal Photosynthetic Activity to Experimental Drought and Warming in a Mediterranean Shrubland

“…He et al [76] recently demonstrated that MODIS-based PRI was sensitive to LUE constrained by water stress due to low soil water content. Magney et al [53] also reported that ∆PRI was more sensitive to water and nutrient limitation but less sensitive to LAI and chlorophyll content throughout the wheat growing season, which enabled ∆PRI to deconvolve the diurnal component from seasonal changes.…”

Chlorophyll Fluorescence Better Captures Seasonal and Interannual Gross Primary Productivity Dynamics Across Dryland Ecosystems of Southwestern North America

“…Alternatively, PRI detects nonphotochemical quenching via changes in the foliar carotenoid pigment pool and thus dynamically tracks changes in photosynthetic activity (Gamon et al, ; Porcar‐Castell et al, ). PRI has been used as a photosynthesis proxy over a range of climate conditions and vegetation types (Gamon et al, ; Gamon, Peñuelas, & Field, ; He et al, ). While previous analyses have explored these emerging proxies in tropical (Lee et al, ), temperate (Yang et al, ), boreal (Walther et al, ), grassland (Jeong et al, ), and cropland ecosystems (Wood et al, ), their ability to capture GPP dynamics across heterogeneous dryland ecosystems remains relatively unknown.…”

The Sensitivity of North American Terrestrial Carbon Fluxes to Spatial and Temporal Variation in Soil Moisture: An Analysis Using Radar‐Derived Estimates of Root‐Zone Soil Moisture

“…Soil moisture is a key variable of the earth system influencing terrestrial water, carbon and nutrient cycling, and the exchange of carbon, water, and energy between the land‐surface and atmosphere. In particular, it impacts meteorological, hydrological, and ecological processes and properties including surface energy balance (Berg et al, ; Ford et al, ; Gallego‐Elvira et al, ; Lin & Cheng, ; Suarez et al, ), land surface albedo (Liu et al, ; Zhang et al, ), soil thermal properties (Juszak et al, ; Sugathan et al, ), runoff (Crow & Ryu, ; Morbidelli et al, ), plant water stress (He et al, ), and resulting vegetation productivity and ecosystem carbon fluxes (Huang et al, ; Jia et al, ; McInerney & Helton, ; Xu et al, ; Xu & Zhou, ).…”